Static Control & Web Cleaning Web cleaners: increasing productivity
and reducing downtime for converters By Iain Cameron, marketing director, Meech International
contents from the first roller, preventing recontamination. These systems are ideal for the removal of small particles (as low as 0.5 micron), but are not designed for applications where the web may become heavily soiled as the adhesive can quickly become tainted and lose its effectiveness. Non-contact technology utilises “blow-
and-vacuum” and boundary layer solutions. Compact and easy to integrate, blow-and- vacuum web cleaners employ air knives on either side of the web to strip the boundary layer and all traces of contamination from the web’s surface. The presence of vacuum airflows ensures that turbulent air is captured and subsequently removed. Boundary layer systems feature high-
WHY SHOULD WEB CLEANERS BE CONSIDERED AN INTEGRAL PART OF A CONVERTER’S PRODUCTION? Combatting issues involving contamination, a web cleaner can help converters increase productivity. Their ability to remove foreign bodies from a web’s surface can reduce downtime and minimise inferior finished product quality, which can lead to excess wastage. The reasons for contaminated webs are
twofold: boundary layers created by a moving web, and the generation of static charges. Both can attract dust, dirt, hair and other assorted particles in the converting equipment’s surrounding area. Boundary layers are caused by the ambient air that the web drags along when in motion. It draws contaminants to the substrate, trapping them beneath the layer and onto the web’s surface, or holding it within the layer. The speed that the web is moving will determine the thickness of the boundary layer – the faster the web, the thicker the layer becomes. Static charges are generated through
the friction or separation between two objects – the fast unwinding of a web, for example, or the web running through or over nip rollers. This can create an electrical charge on the material surface that will attract contaminants.
WHAT ARE THE DIFFERENT TYPES OF WEB CLEANERS AND HOW CAN CONVERTERS DETERMINE WHICH WILL WORK BEST FOR THEM? Web cleaning technology comes in two forms – contact and non-contact. Deciding on the most practical system depends on the web materials being processed, the
16 March 2019
application, the flexibility required by the converting line, and the available budget. Designed to make contact with the web
and break the boundary layer, contact cleaners will incorporate either vacuum technology or adhesive rollers. The former comes in various designs. One employs a low-friction method, utilising a highly- polished steel faceplate, for example, which makes contact with the web, breaking the boundary layer and releasing the contaminants, which are subsequently vacuumed away.
speed, non-contact rollers which rotate at a distance between 0.5 and 1mm from the surface of the web. Their design is optimised for the rollers to generate a high-speed boundary layer, the greater energy of which destroys the boundary layer carried by the incoming web. This exposes even the smallest particles on the web to a very powerful cleaning force, which sees the rollers lift and remove the particles from the web and carry them to a vacuum extraction chamber.
HOW CAN STATIC GENERATION BE COMBATTED?
Alongside contamination attraction, static can result in a number of other issues, such as poor print quality, tiny holes that appear in extruded film, or blockages in machinery equipment. Its elimination should be a fundamental part of the quality control measures adopted by any converter. In fact, combining a web cleaner with an effective static control solution can allow for the most pristine of webs, guaranteeing print quality is maintained and health and safety is observed. Active static control provides the most
Other vacuum contact systems contain brushes that free debris before vacuuming – this can be an effective approach when larger particles need to be removed from heavily contaminated webs but can harm the surface of sensitive webs, and require regular cleaning to reduce the risk of cross-contamination. Adhesive roller cleaners incorporate
twin elastomer rollers, which are in contact with the full width of the web, physically lifting debris from the web’s surface. The contaminants are then transferred to a second roller with a high adhesive mass, which removes the
effective means of neutralising charges. The technology uses ionisation, which employs high voltage AC or “pulsed” DC to produce ionised air to neutralise surface charges. The voltage is fed to an array of titanium emitter pins mounted on an ionising bar, creating a high-energy “ion cloud” of positive and negative ions. In its AC guise, as the AC cycle changes, positive or negative ions are produced in approximately equal quantities, and a statically-charged surface of either polarity passing close to the cloud is quickly neutralised. Installing ionising bars and web cleaners can ensure you are meeting health and safety standards and encounter minimal quality control issues.
meech.com
convertermag.com
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